Despite impressive recent advances in adolescent drug abuse treatment research, including the manualization and evaluation of theory-based interventions and a preliminary understanding of how these treatments create in-treatment and post-treatment gains, almost nothing is known about the long-term effects of adolescent-specific drug abuse treatment. This application proposes the first controlled long-term study of two state-of-the-science, commonly-practiced treatment modalities -- one outpatient and the other residential -- for adolescent drug abuse. These treatments are being tested in a still active comparative clinical trial being conducted by investigators at the University of Miami Center for Treatment Research on Adolescent Drug Abuse. This ongoing study is the first randomized trial comparing the therapeutic effects and relative benefit-costs of any outpatient approach with a residential adolescent drug treatment. Impressive follow-up data capture rates, promising preliminary 12-month outcome findings from this trial, and the absence of empirical evidence to guide researchers, practitioners or policy makers on the long-term outcomes of adolescent drug treatment all support our aim to study the longer-term impacts of these interventions. The proposed long-term follow-up study will follow 140 adolescents and their parents randomized to either outpatient or residential treatment. Youth and their parents/guardians will be assessed at 2, 3, and 4-year follow-up periods on a range of drug use, family and psychosocial functioning, as well as economic evaluation measures. The study has three aims: 1) To compare the long term effectiveness of residential treatment with outpatient, family-based treatment in ameliorating drug use, co-morbid symptoms, and criminality among dually diagnosed adolescents. 2) To examine the relationships among predictors (i.e., family functioning, peer, educational/vocational functioning and involvement in post-treatment services drug use) and outcome variables (i.e., drug use, co-morbid symptoms, and criminal behavior) during the four-year post intake period. 3) To contrast the total and net long-term monetary benefits of the residential treatment and the outpatient family based treatment.